A multi-mode optical fiber is used to transmit optical waves in a plurality of modes at a same time. Because optical waves in different modes interfere with each other, high inter-mode dispersion is caused, and a relatively small capacity of information can be transmitted, the multi-mode optical fiber is usually used in a small-capacity and short-distance optical signal transmission system. A single-mode optical fiber can transmit an optical wave in only one mode. Because the optical wave in only one mode is transmitted, there is no problem of inter-mode dispersion in the single-mode optical fiber. Therefore, the single-mode optical fiber is used in a large-capacity and long-distance optical signal transmission system.
A fiber core of the multi-mode optical fiber is relatively large, and is usually 50 micrometers (um). However, a core diameter of a single-mode optical fiber is small, and is usually 9 μm or 10 μm. A housing for packaging an optical transmitter module provided in other approaches is adapted to the multi-mode optical fiber. It becomes particularly important to design, based on a great advantage of the single-mode optical fiber over the multi-mode optical fiber in terms of optical signal transmission, a housing that is for packaging an optical transmitter module and that can be adapted to the single-mode optical fiber.